Tanio Koba M9 airsoft Twist Tightbore Barrel. Twist in barrel creates a more accurate BB shot down the field, increasing both accuracy and range. For use with hop-up (previously corrected) guns. Ideal to use with airsoft guns that shoot under 350 FPS or around 1 joule. Great for stock Marui as well. Not recommended for guns shooting over 350 FPS. Easy upgrade for your Tokyo Marui gas-blowback pistol.